Method of making abrasive articles



Patented Nov. 15, 1938 UNITED STATES PATENT OFFICE METHOD OF MAKINGABRASIVE ARTICLES Raymond C. Benner and George J. Easter, Niagara Falls,N. Y., assignors to The Carbon!!!- dum Company, Niagara Falls,

tion of Delaware N. Y., a corpora- No Drawing. Application September 11,1937,

- Serial No. 163,436

3 Claims.

that it is extremely diflicult to obtain a good bond for diamonds. Thisis largely due to the difficulty of obtaining a bond which willthoroughly wet or coat the surface of the diamond particles andconsequently promote the close adherence or adhesiveness between theabrasive and the bond. In the use of metal in its powdered or cast form,the adhesion between bond and diamond has never been as satisfactory asmight be desired. The diamond particles have not been thoroughly wettedand have to a large extent been merely gripped by the surrounding metalbond without complete wetting of the interfaces taking place. Articlesso made therefore have not shown the high efliciencies and durabilitywhich are so much to be desired.

One of the main objects of this invention-is the metallic bonding ofdiamond particles in such a way that the diamond particles are morecompletely wetted by the bond and a resulting article obtained ofimproved cutting ability and characteristics, as well as prolonged life.We accomplish this by the use of metal amalgams as the wetting andbonding materials for the dia- 'monds according to the methods hereinset forth,

which methods play an important part in the successful formation of sucharticles.

Another important feature of the present invention is the provision as awetting and bonding material for diamonds of an amalgam relativelyinexpensive and therefore extremely economical for general industrial orcommercial application. For this purpose we make use of amalgamscontaining substantial amounts of base metals, and at times even theamalgam is composed entirely of base metals.

The amalgams which we use can all be easily made by simple intimateadmixing of the metal or metals with mercury, although due to thedifliculty of obtaining some of the metals in powdered form we usuallyprefer to carry out the amalgamation indirectly by electrolyticdecomposition of the metallic salts of-the metal which we desire toamalgamate using mercury as a cathode or a similar decomposition of amercury salt using the metal as'a cathode, depending upon theavailability of the respective raw materials. Numerous other methods ofobtaining the amal- More particugams may be used, but the above twogeneral methods, especially the electrolytic method, are given asexamples because of their simplicity and their applicability topractically all of the amalgams we may care to make. In forming theamalgams we use additional mercury over that required to form the solidamalgam-of the metal and sufiicient to obtain an amalgam in pasty or.semi-liquid condition, often containing excess mercury. Although theamalgam is usually made up in small quantities just prior to use, wesometimes have found occasion to make it up some in which event it.isdesirable to maintain the amalgam under electrolytic potential toprevent its deterioration in any way before use.

Some of the metals which .we are able to amalgamate by one or more ofthese methods are potassium, sodium, barium, calcium, zinc, tin, lead,bismuth, copper, antimony, silver and gold. Theamalgams which we useare. usually combinations of more than one of the above metals in whichcase we generally proceed by successive electrolytic amalgamation of thevarious constituent metals of the desired final amalgam. In this processafter amalgamation of one of the metals for a predetermined period oftime the first constituent metal to'be amalgamated and which has actedduring its amalgamation as the cathode is removed, the second metal tobe amalgamated is then placed-in the same amalgamation chamber as thecathode and the operating conditions readjusted to those best suited forits amalgamation and the operations resumed until the.

desired amount of this metal is present in the amalgam. After all of thedesired constituent metals have served as cathodes for the periodsnecessary to amalgamate the required amounts of each metal desired to bein the final alloyamalgam, the operation is complete. During the laterportion of the operation, as the amalgam becomes pasty rather thanfluid, it is desirable to employ mechanical stirring'of the amalgam moreor less continuously in order to cause the depositing metal to bedispersed evenly throughout the amalgam rather than plated onto it as aseparate surface layer. Heat may also be applied as required to keep theamalgam workable at concentrations which result in the formation of apowderable texture when cold. This electrolytic process of amalgamationis quantitatively very accurate and practically any desired compositionof alloy-amalgam may be obtained in this way.

' After the amalgam has been made and is ready to use in paste or liquidform, we then thoroughly mix into the mass a quantity of diamondparticles, continuing the mixing until we are sure the diamonds areuniformly distributed throughout the amalgam. Instead of using diamondsas the tinie before using it as the bond br wetting agent,

coating the diamond particles with a silver-copper amalgam, thereafteradding metal powder free from mercury to the coated diamonds and moldingand sintering the mass to shape.

3. The process of manufacturing metal-bonded abrasive articles whichcomprises moistening.

non-metallic abrasive particles with a wettingout agent which assiststhe wetting of said particles by amalgams, coating said abrasiveparticles with an amalgam, thereafter mixing the amalgam-coatedparticles with additional metallic bond free from. mercury to form anabrasive mixture, pressing and sintering said mixture to the 5 desiredshape. 7

RAYMOND C. BENNER. GEORGE J. EASTER.

